North American Philips Corporation

David C Greene

Edwin R Meyer

Larry G Phillips

A method and apparatus for synchronizing a received television signal to a subcarrier locked signal is provided. The apparatus includes a comparison block for determining whether the received television signal and subcarrier locked signal are related by a predetermined fixed frequency relationship and for providing indications of the same, and a signal generation block for dividing down the subcarrier locked signal according to the predetermined fixed frequency relationship so as to provide an output signal which is synchronized with the subcarrier locked signal, and at a frequency determined according to the fixed frequency relationship when the signals are related. The apparatus is particularly useful in PIP applications where the received television signal is a horizontal signal and the subcarrier locked signal is a four times multiple of the subcarrier frequency. The comparison block preferably includes a counter and a windowing circuit for determining whether edges of horizontal signal pulses are received within or outside a predetermined time window, and a decision circuit for determining whether the occurrences (counts) of in and out of window edges are indicative of related or unrelated signals. The entire apparatus preferably includes only flip-flops, simple logic gates such as AND, NAND, or OR gates, inverters, multiplexer switches, and resettable counters. The apparatus also preferably further includes a standard combination of flip-flops and a NAND gate for providing a synchronized horizontal reset output signal when the comparison block determines that the received horizontal clock and the subcarrier locked clock are not related.

Apparatus and method for generating a horizontal reset signal

Apparatus and methods for remodulating digital luminance and color difference components for display as PIP information, or together with other composite video components for multi-PIP and test pattern applications are disclosed. A digital encoder is used for conducting a digital quadrature modulation on the color difference components and for digitally adding the luminance signal thereto prior to the converting of the remodulated information into an analog format. Preferably, the digital video information output by the encoder is in the form Y1+(R-Y)1, Y1 +(B-Y)1, Y2-(R-Y)1, Y2-(B-Y)1, Y3+(R-Y)2. Y3+(b-Y)2, Y4 -(R-Y)2, . . . , where Y is the luminance component, R-Y and B-Y are color difference components, and where the numbers index received samples of the video components with the luminance component being sampled at twice the frequency of the color difference components. Where digitally modulated composite video is desired, fixed black level, burst, and background values are multiplexed with the active R-Y and B-Y signals, while fixed sync tip, black level, and background values are multiplexed with the active Y signals prior to encoding.

Apparatus and method for creating digitally remodulated video from

A stabilized gated oscillator that provides pulses at a predetermined repetition rate in phase coherence with a gating signal includes a ceramic resonator in a feedback resonant circuit between the output terminal and the input terminal of a linear amplifier. The resonant circuit, which establishes the repetition rate, is constructed to provide an oscillator frequency in a frequency range between two resonant frequencies of the ceramic resonator wherein the ceramic resonator acts as an inductance.

Stabilized gated oscillator utilizing a ceramic resonator

A gated oscillator circuit for generating a sampling signal for digitally processing television signals, uses an LC oscillator to achieve, high frequency stability and reduced edge jitter. Circuitry is provided on both sides of a tank circuit in the oscillator for decoupling the tank circuit from other active circuit elements thereby enhancing the frequency stability.

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Knoxville, TN, United States of America

David C Greene